This study is a prospective, randomized, multicentre, study concerning the influence of local treatment on the patients with synchronous metastasized breast cancer. Patients will be stratified at inclusion according to the centre, the menopausal status (pre-menopausal, post-menopausal), the hormone-receptor status (ER-/PR-/not determinable; any PR and/or Er+), the HER-2 status (positive vs. negative/not determinable), the grading (G1/G2/not determinable vs. G3), location of metastases (visceral ± vs bone only), organs with metastases (single organ vs multiple organs) and use of first line chemotherapy (anthracycline ± vs. taxane vs others). Thereafter patients will be randomly assigned to receive either local therapy of the breast (lumpectomy or mastectomy + axillary surgery /± radiotherapy) versus no local therapy. Systemic therapy will be administered at the centers policy.